RE: 264 Series and their chips

Were both in production or just the R4? If only the R4 was seen for the
most part then it might have been the Back Bias generator /P0 change I
mentioned earlier.

-----Original Message-----
From: owner-cbm-hackers@musoftware.de
[mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Gerrit Heitsch
Sent: Sunday, August 14, 2011 2:39 PM
To: cbm-hackers@musoftware.de
Subject: Re: 264 Series and their chips

On 08/14/2011 08:20 PM, Bil Herd wrote:
> Ah, forgot about the speed, we didn't kick that on till later in the
> design cycle.
>
> I would think that the 75/85 versions should work at double clock as
> in many ways it's access times are already running at that speed, it
> will also depend on supporting  chips speeds to some degree too I think
, I.E.
> 150ns DRAMs would help, etc.  I would think that one of the
> problematic areas would be getting the address out and through the
> MUX/257's in time for /RAS, and the R/W line in time for /WE to be valid
for a  clean write.

If you can still find 41464 RAMs, they are mostly from old VGA cards and
those usually use 120ns and faster. So RAM speed shouldn't be a problem.

Another way would be to do what I did with a C64, replace the DRAMs with a
128Kx8 SRAM. In the C64 the VIC supplies multiplexed addresses already so
I had to demultiplex them with a 74HCT573 first and use _RAS or'ed with
_CAS as chip select for the RAM. Since TED doesn't supply multiplexed
addresses and _CAS is not routed through the PLA the whole setup should be
way easier, possibly needs only _CAS as chip select.

Currently I don't have a spare 8500 to try this with though.

Do you happen to remember the difference between the 8501R1 and the
8501R4? I couldn't find any information concerning what was changed
between R1 and R4.

  Gerrit



>
> Bil
>
> -----Original Message-----
> From: owner-cbm-hackers@musoftware.de
> [mailto:owner-cbm-hackers@musoftware.de] On Behalf Of Gerrit Heitsch
> Sent: Sunday, August 14, 2011 1:45 PM
> To: cbm-hackers@musoftware.de
> Subject: Re: 264 Series and their chips
>
> On 08/14/2011 07:17 PM, Bil Herd wrote:
>> We made the original 7501/8501 with a 6510 and a 74ls74 on a small
>> tower, there wasn't a dependency on the excat mapping of the I/O
>> p[ort at the time, but should be something you can put together.
>
> Even if the difference between I/O-Ports (6510 = P0-P5 and 7501 =
> P0-P4,P6-P7) can be worked around (patching all KERNAL locations and
> ignoring tape functions), the question is, will the 6510 or the 8500
> work with 1.77 MHz the 8501 runs at part or all of the time? I don't
> remember ever seeing a 6510A and the 6510T from the 1551 which
> supposedly runs on 2MHz seems to be even more rare than a 8501.
>
> BTW: In a PAL 264 system, you can push the CPU to 2.2MHz by setting
> TED to 'display off' and 'NTSC'. You don't get usable video output,
> but double speed compared to normal. Never crashed on me, but I always
> had heatsinks on TED and CPU back then.
>
>
>
>>
>> Bil Herd
>>
>> -----Original Message-----
>> From: owner-cbm-hackers@musoftware.de
>> [mailto:owner-cbm-hackers@musoftware.de] On Behalf Of
>> Ruud@Baltissen.org
>> Sent: Saturday, August 13, 2011 12:23 PM
>> To: cbm-hackers@musoftware.de
>> Subject: Re: 264 Series and their chips
>>
>> Hallo Gerrit,
>>
>>
>> Have you ever thought about replacing the 8501 with a 8502 from a
>> C128? So far I found four differences:
>> - the 8501 has this MUX input (or output? I have no idea what it
>> does) which the C128 lacks
>> - the 8502 has an "extra" NMI input compared to the 8501
>> - the 8501 lacks the P5 I/O pin, the 8502 P7
>> - pinout doesn't match
>> If the MUX gate doesn't spoil things, what about using the 8502?
>> Regarding P5/P7: you either don't use the cassette recorder anymore
>> or adjust the bits of the Kernal.
>>
>> Just my two cents...
>>
>>
>> --
>>       ___
>>      / __|__
>>     / /  |_/     Groetjes, Ruud Baltissen
>>     \ \__|_\
>>      \___|       http://Ruud.C64.org
>>
>>
>>
>>
>>
>>
>>
>>          Message was sent through the cbm-hackers mailing list
>>
>>          Message was sent through the cbm-hackers mailing list
>>
>>
>
>
>         Message was sent through the cbm-hackers mailing list
>
>         Message was sent through the cbm-hackers mailing list
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>


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